Retractable pen



FIG. 1 is a right side elevational view of our design;

FIG. 2 is a front elevational view of our design;

FIG. 3 is a rear elevational view of our design;

FIG. 4 is a bottom view of our design; and,

FIG. 5 is a top view of our design.

The writing tip depicted by means of broken lines in FIGS. 1 through 4 has been shown for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for an retractable pen, as shown and described. 